Currently, in order to improve system integration or perform zoning according to different functions, a device cabin (such as a subrack or a plug-in frame) of some electronic communications devices is divided into a front part and a rear part that are orthogonal to each other. That is, a backplane is disposed in a specific position in the middle of or inside the device cabin, and boards are disposed before and after the backplane. Generally, a front board and a rear board form an orthogonal structure. The front board is a service processing board, the rear board is an interface board for implementing a switching function, and the rear board needs to output plenty of cabling interfaces because the rear board is responsible for the switching function.
In the existing orthogonal structure, the rear board needs to be disposed with an output port, and also needs to implement hot swap. Therefore, a fan that is disposed in the rear part to dissipate heat for the rear board cannot be disposed behind the rear board. General solutions include When the rear board is placed horizontally, the fan is disposed on an upper side and a lower side of the rear board, and air passes through both sides of a group of rear boards and separately gets into fan components located in an upper position and a lower position; and when the rear board is placed upright, a fan component is disposed on the top of the rear board, and air passes through both sides of each rear board and converges into the fan component at the top. In both of the foregoing two solutions, the following heat dissipation manner is applied. Air ducts are disposed on both sides of the rear board, and air is taken in from both sides of the rear board and then gets into the fan component.
However, in the foregoing heat dissipation manner, the rear board generally has complex air ducts with a long path, and system resistance is large. Consequently, a heat dissipation capability of the rear board is limited, and a high-performance fan is generally required to meet a heat dissipation requirement of the rear board. Moreover, the foregoing form of air ducts of the rear board makes cascaded heating exist between panel interfaces. In a case where multiple optical interfaces exist, as affected by a high temperature of an upstream port, it is difficult for a downstream port to dissipate heat, which makes it difficult to enhance the heat dissipation capability of the rear board. In addition, when air is taken in from both sides of the rear board, air duct space needs to be reserved on both sides of the rear board, which restricts dimensions of the rear board and therefore restricts the number of output ports of the rear board.